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    <title>Document</title>
    <script>
        function unique(arr) {
            // 新数组
            var res = []
            for (var i = 0; i < arr.length; i++) {
                if (res.indexOf(arr[i]) == -1) {
                    res.push(arr[i])
                }
            }
            return res
        }
        var demo = unique(['c', 'a', 'z', 'a', 'x', 'a', 'x', 'c', 'b'])
        console.log(demo)
    </script>
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